Loans - Schedule of Analysis of Past due Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	$ 1,039	$ 2,094
Current Loans	326,473	370,495
Total Loans	327,512	372,589
Commercial Real Estate [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Current Loans	186,021	191,645
Total Loans	186,021	191,645
Commercial Land Development [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		303
Current Loans	1,847	1,884
Total Loans	1,847	2,187
Commercial Other [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Current Loans	34,646	30,508
Total Loans	34,646	30,508
Residential Real Estate First Mortgages [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	977	1,561
Current Loans	67,264	106,523
Total Loans	68,241	108,084
Residential Real Estate Construction [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Current Loans	3,671	2,097
Total Loans	3,671	2,097
Consumer Home Equity and Lines of Credit [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	60	228
Current Loans	32,304	35,926
Total Loans	32,364	36,154
Consumer Other [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	2	2
Current Loans	720	1,912
Total Loans	722	1,914
Loans Past Due 30-89 Days [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	652	1,687
Loans Past Due 30-89 Days [Member] | Residential Real Estate First Mortgages [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	650	1,470
Loans Past Due 30-89 Days [Member] | Consumer Home Equity and Lines of Credit [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		215
Loans Past Due 30-89 Days [Member] | Consumer Other [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	2	2
Loans Past Due 90+ Days [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	387	407
Loans Past Due 90+ Days [Member] | Commercial Land Development [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due		303
Loans Past Due 90+ Days [Member] | Residential Real Estate First Mortgages [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	327	91
Loans Past Due 90+ Days [Member] | Consumer Home Equity and Lines of Credit [Member]
Loans, Notes and Certificates, and Loan Servicing Rights [Line Items]
Past Due	$ 60	$ 13